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Biomedical subjects

A Castenholz

Publications and source records attributed to A Castenholz.

At least 19 recordsLinked to original sources
PubMed1998

Functional microanatomy of initial lymphatics with special consideration of the extracellular matrix.

In current conceptions on the functional morphology of initial lymphatics, the extracellular matrix (ECM) as an integral part of the lymphatic vascular wall has not been duly considered. In the present study based on scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) of tongue tissue in rats, new insights were obtained into both the architecture of the fibrous network of the ECM and its functional features. A digestion technique was applied, by which the endothelium of initial lymphatics was detached thereby allowing a direct view of the ECM from both sides. Fluorescent latex particles and liposomes were used as indicators of transmural permeability, whereas labeled macrophages served as a model for penetrating cells. The two layers of the lymph vascular wall were also examined under experimental edema conditions with tissue pressures ranging from 10 to 150 mmHg. A concept is proposed which considers the histomechanics of the initial lymphatics with the surrounding connective fiber tissue including the structural basis for the permeability of the lymphatic vascular wall. The role of the ECM as a supporting element and prefilter for the lymphatic endothelium is emphasized.

Animals↗
PubMed1996

Casting methods of scanning electron microscopy applied to hemal lymph nodes in rats.

Hemal lymph nodes of the para-aortic group in rats were examined by scanning electron microscopy (SEM) using the corrosion cast technique. The vasoarchitecture of hemal lymph nodes was described in cast specimens filled from the abdominal aorta. A dense system of capillaries arranged in the mode of a meshwork could be represented in the nodal cortex. The postcapillary venule (PCV) with wide vascular lumina provided the prevailing vessel type of the deep cortex. Sphincter-like narrowings of the capillary lumen appeared at the sites where capillaries merged with the PCV. These vascular segments were interpreted as structures controlling the hemodynamics of the joining PCV thereby providing appropriate conditions for homing lymphocytes. No evidence was obtained from the casts for an open circulation in hemal lymph nodes. The intranodal lymphatic pathways were studied in specimens interstitially injected with resin. The fine lymphoid tissue spaces were characterized by special cast patterns reflecting the structural differentiation of certain nodal compartments. Afferent lymphatics could be clearly identified in casts with a retrograde filling from the subcapsular sinus. Very spacious intermediary sinuses and wide meshed medullary sinuses could be represented in those casts as well, thus allowing ample space for the encounter of large macrophages with red blood cells.

Animals↗
PubMed1996

Fluorescence microscopic studies on hemal lymph nodes in rats: a new immunobiological concept.

Hemal lymph nodes are characterized by a high content of blood cells most of them in different stages of erythrophagocytosis. These peculiar structures are not well understood up to now regarding their functional morphology. Above all, their biological relevance, especially to the phenomenon of disintegration of one's own blood cells, has eluded conclusive explanation so far. In the present study, hemal lymph nodes of 45 rats of the perirenal group were investigated by means of confocal laser fluorescence microscopy (CLSM) in combination with three fluorescent markers: latex standard particles, liposomes and autologous erythrocytes. Each marker briefly entered the hemal lymph nodes when injected into the kidney, whereas no notable migration took place after intravenous injection. Besides direct connections between hemal lymph nodes and the homolateral kidney, the study also revealed lymphatic communications with the contralateral kidney. Each marker was ingested by nodal macrophages, most of them surrounded by red blood cells (rosette formation) and laden with the by-products of cellular disintegration (erythrophagocytosis). Intimate contact of lymphocytes with macrophages as an expression of special interaction (emperipolesis) between both types of cells was frequently observed. A new concept is proposed, which ascribes to the hemal lymph nodes an important immunobiological role for the recognition of antigenic properties of one's own red blood cells permanently released by the kidney. The information macrophages obtain from these cells is presented to lymphocytes, which, in turn, initiates suppresser immune reactions. Under normal conditions, this mechanism of cellular identification and surveillance serves to preserve self-tolerance of the defense system against permanent renewal of one's own red blood cell population during a life time. In this way, an auto-aggressive immune anemia is circumvented.

Animals↗
PubMed1995

Examination of injected specimens by confocal laser scanning microscopy and scanning electron microscopy.

Although corrosion casts commonly examined by scanning electron microscopy (SEM) offer good insights into the general arrangement of the microvasculature of certain organs, no information can be obtained from such specimens on special morphological data or dynamic events. Thus, most investigators are obliged to make their interpretations of cast structures only on the basis of indirect criteria. A synopsis, which considers the most important data in that respect, is given for the blood and lymphatic microvessels. Moreover, a methodological approach is introduced, based on the application of fluorescent resin, which allows the examination of cast structures in uncorroded specimens together with the surrounding tissue by confocal laser scanning microscopy (CLSM). When two differently stained resins are injected at different sites, e.g., Mercox-fluorescent yellow into an artery and Mercox-rhodamine into the interstice, blood vessels and lymphatics can be well distinguished. In lymph nodes, the system of lymphoid spaces and that of intranodal sinuses can be separately represented with the same technique. Applications and advantages of the CLSM method, which is a useful tool for an extended interpretation of corrosion casts in SEM, are shown in cast specimens from tongue, skin, and liver in rats. In this study, both corroded and uncorroded specimens were considered. In addition, a new approach is demonstrated which combines casting technique and fluorescence microscopy with investigations carried out under experimental conditions. This allows the examination of microvascular casts together with labelled cells in liver and spleen in a state of phagocytosis.

Animals↗
PubMed1993

The sublingua and tongue of Tupaia (Scandentia, Mammalia): a scanning electron microscope study.

The surface morphology of the tongue and the sublingua in Tupaia belangeri was examined both under the dissection microscope and with the scanning electron microscope. Shape and structural differentiation of the sublingua and the anterior ventral part of the tongue are described. Special types of papillae were found on the lingual segment of the keel, along the serrated edges of the sublingua, and at the apex linguae. The findings are discussed with respect to the special conformation of the oral cavity of Tupaia and in relation to the evolutionary and functional significance of the tongue and the sublingua in this species.

Animals↗
PubMed1992

[Contribution of prelymphatic structures to lymph drainage].

Vitalmicroscopic findings confirm the existence of a "low resistance pathway" for the transinterstitial fluid movement from the pillaries to the initial lymphatics. One part of this prelymphatic system is represented by submicroscopical spaces along the connective tissue fibres between ground substance (high resistance pathway) and fibre surface. The other part is represented by a network of prelymphatic tissue channels which are open connected with the initial lymphatic system.

Humans↗
PubMed1991

Light and electron microscopy of the structural organization of the tissue-lymphatic fluid drainage system in the mesentery: an experimental study.

Supplementing vital microscopy and histophysiology, we examined using combined light and electron microscopy the tissue fluid-lymphatic drainage system of the mesentery isolated from guinea pigs, rabbits, and tree shrews. In silver impregnated tissue, different types of lymphatics and blood vessels were able to be distinguished along with argyrophilic and argyrophobic structures in the connective tissue. Some initial lymphatic pathways were interrupted by non-endothelialized tissue zones thus forming separate but discrete vascular "islands". After carbon labeling of the lymphatic collectors, carbon particles were seen to escape from the initial lymphatic lumen at various sites. Electron microscopy revealed wide apertures in the lymphatic endothelial cells of these microvessels. These morphological findings support the concept of an "open" prelymphatic-lymphatic system in the mesentery. The special histometrical features exhibited by a flat membranous organ like the mesentery are discussed in terms of physiologic function of mesenteric tissue fluid transport.

Animals↗
PubMed1989

[New knowledge of the structural principle of lymph formation].

The structural conditions in the zone of transition from the tissue to the lymphatics are described on the basis of electron microscopic (especially scanning electron microscopic) and light microscopic results. Here, the interstitium with its fiber organization and the system of prelymphatic channels as well as the wall characteristics of the initial lymphatics and precollectors are given particular consideration. The flow conditions, the stretching ability and the permeability of the very fine lymphatics are investigated in the model of the rat tongue by means of a special vital microscopic technique using various labelling substances. Against the background of the morphological and rheological findings, the question of lymph formation is analysed on the basis of new hypothetical criteria for the mechanisms involved.

Animals↗
PubMed1989

Interpretation of structural patterns appearing on corrosion casts of small blood and initial lymphatic vessels.

Structures imprinted on the corrosion casts of blood and lymphatic microvessels are examined by correlative scanning electron microscopy of corroded casts and fixed tissue. Replicas of the endothelial nuclear portions and cell boundaries and the plastic bands surrounding the casts of terminal blood vessels are demonstrated. In small lymphatics the replication of valve structures, interendothelial open junctions and direct prelymphatic connections is shown. The different imprint patterns are examined in regard to their morphological significance and under methodical aspects.

Animals↗
PubMed1987

Structural and functional properties of initial lymphatics in the rat tongue: scanning electron microscopic findings.

The luminal and outer wall morphology of the initial lymphatics in the rat tongue were demonstrated using scanning electron microscopy (SEM) after tissue perfusion with pressures up to 300 torr, topical heat and histamine administration. The findings emphasize the structural and functional importance of the reticular fiber network of the basement lamina (in contradistinction to single "anchoring filaments") as a supportive framework for lymphatic endothelium and a major regulatory role in tissue volume control. Increased tissue pressure was associated with dilatation of initial lymphatics which was maximal at approximately 60 torr. Higher pressures (up to 300 torr) did not damage the vessels. This vasodilatory response of the initial lymphatics was even more evident when tissue swelling was hindered by externally applied plaster "bandage". Under SEM, protruding and branched cells were conspicuous in otherwise flat lymphatic endothelium. These cells may have contractile properties and with pronounced dilatation, thermal injury and application of histamine these cells probably contract, thereby creating large gaps at the site of open junctions.

Animals↗
PubMed1986

Corrosion cast technique applied in lymphatic pathways.

The paper deals with methods and results of the microcorrosion cast technique in lymph angiology. For the representation of the special organization of the lymph vascular system including the initial vascular structures, intranodal pathways, bigger collectors, and lymph trunks, the application of various injection techniques is necessary. The interstitial injection of Mercox proves to be suitable to show the initial lymphatics and prelymphatic spaces. Similarly, the intranodal injection makes visible the system of the lymph sinuses and the spaces of the reticular tissue in this organ. Casts of bigger collecting vessels, lymph trunks, and thoracic duct can be obtained by direct injection of the resin into the vascular lumen. Thus, these techniques enable to make visible the structural details of the cast preparations of all parts of the lymphatic system.

Animals↗
PubMed1985

[Functional morphologic mechanisms of lymph transport].

The phenomenon of the lymph flow in the initial lymphatics and lymphangions of collecting vessels has been studied. Special attention was paid to the structural features and functional mechanisms of the lymphatic vascular system as well as the influence of extravascular factors on the lymphatic flow. In this context, a survey of the current knowledge of functional-morphological research in lymphology is given which may lead to a better understanding of a disturbed lymph flow under pathophysiological conditions.

Action Potentials↗
PubMed1985

The endothelium of initial lymphatics during postnatal development of the rat tongue.

The luminal surface of the subepithelial lymphatic plexus in the tongue of rats was investigated with SEM at different stages of postnatal development. In newborn and infant animals prominent and branched endothelial cells exhibit a conspicuous phenomenon producing a very irregular inner profile of the vascular wall. Among these cells the spindle-shaped type proves to be an essential component of the valve structures already found in few-day-old animals. There are also prominent cells with a polygonal appearance resembling histioblasts which form with their manifold processes, that partly extend into the lumen, an interlacing cellular pattern. The special morphological characteristics of the endothelium of the initial lymphatics already occurring in early postnatal development point to several particular functional activities such as controlled permeability, contractility, phagocytotic property, and demonstrate the exceptional position of this kind of vessel among the structures of the lymph- and blood-draining system.

Aging↗
PubMed1984

Scanning electron-microscopic study of Reissner's fiber in the caudal spinal cord of the cat and rabbit.

The caudal portion of Reissner's fiber was examined by scanning electron microscopy (SEM) in the spinal cord of the cat and rabbit. In some preparations of both species the fiber displayed in the sinus terminalis of the central canal either stump-like terminations or structural modifications such as knot-like swellings and convolutions. In the same area homogeneous material could also be found, which obviously originated from the disintegrating fiber.

Animals↗
PubMed1984

Morphological characteristics of initial lymphatics in the tongue as shown by scanning electron microscopy.

The subepithelial lymphatics of the rat tongue were examined by scanning electron microscopy in interstitially fixed tissue and corrosion casts. In tissue preparations fixed at low interstitial pressures, the endothelium exhibits broad and flat cells with serrate endothelial borders. In the course of the intercellular border system, simple junctions and overlapping zones occur. The latter have the appearance of pocketings. In tissue fixed at high interstitial pressures of up to 75 mm Hg, many endothelial cells become bulged and show long or short processes. The pocketings disappear and are replaced by openings which are covered by a fine fibrous network surrounding the vascular wall. The plexus-like arrangement of the subepithelial lymphatics of the tongue can well be demonstrated in corrosion casts. The vascular system consists for the most part of capillary vessels anastomosing like a net or terminating blindly in rootlets. The imprints of endothelial nuclei and cellular borders as well as of valve patterns in the casts enable a good differentiation between vascular and interstitial structures. The findings on the special morphological characteristics of the initial lymphatics are also discussed under functional aspects.

Animals↗